We can't really do anything about whether it unfurls or not. Indeed this is returning, quite astonishingly, a WAP XML response by default:
XML:
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE html PUBLIC "-//WAPFORUM//DTD XHTML Mobile 1.0//EN" "http://www.wapforum.org/DTD/xhtml-mobile10.dtd"><html xmlns="http://www.w3.org/1999/xhtml">
But I think the better solution here is to just embed it like a normal Facebook post, rather than relying on unfurling which is a change we've made already for the next release.